Note 9 - Segment Information - Geographic Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net revenues	$ 57,160	$ 54,579
BRAZIL
Net revenues	$ 15,532	$ 13,410
BRAZIL | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	27.20%	24.60%
SOUTH AFRICA
Net revenues	$ 6,534	$ 7,444
SOUTH AFRICA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	11.40%	13.60%
MEXICO
Net revenues	$ 5,287	$ 5,360
MEXICO | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	9.20%	9.80%
CHINA
Net revenues	$ 3,279	$ 2,442
CHINA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	5.70%	4.50%
INDIA
Net revenues	$ 2,730	$ 2,247
INDIA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	4.80%	4.10%
JAPAN
Net revenues	$ 2,206	$ 2,424
JAPAN | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	3.90%	4.40%
CANADA
Net revenues	$ 2,104	$ 1,934
CANADA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	3.70%	3.50%
AUSTRALIA
Net revenues	$ 764	$ 886
AUSTRALIA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	1.30%	1.60%
TURKEY
Net revenues	$ 67	$ 63
TURKEY | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	0.10%	0.10%
International [Member]
Net revenues	$ 38,503	$ 36,210
International [Member] | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Percent of consolidated net revenue	67.30%	66.20%